This invention relates to systems and methods for processing blood, e.g., for filtration, pheresis, or other diagnostic or therapeutic purposes.
There are many types of continuous and intermittent blood processing systems, each providing different therapeutic effects and demanding different processing criteria.
For example, hemofiltration emulates normal kidney activities for an individual whose renal function is impaired or lacking. During hemofiltration, blood from the individual is conveyed in an extracorporeal path along a semipermeable membrane, across which a pressure difference (called transmembrane pressure) exists. The pores of the membrane have a molecular weight cut-off can thereby pass liquid and uremic toxins carried in blood. However, the membrane pores can not pass formed cellular blood elements and plasma proteins. These components are retained and returned to the individual with the toxin-depleted blood. Membranes indicated for hemofiltration are commercially available and can be acquired from, e.g., Asahi Medical Co. (Oita, Japan).
After hemofiltration, fresh physiologic fluid is supplied to toxin-depleted blood. This fluid, called replacement fluid, is buffered either with bicarbonate, lactate, or acetate. The replacement fluid restores, at least partially, a normal physiologic fluid and electrolytic balance to the blood. Usually, an ultrafiltration function is also performed during hemofiltration, by which liquid is replaced in an amount slightly less than that removed. Ultrafiltration decreases the overall fluid level of the individual, which typically increases, in the absence of ultrafiltration, due to normal fluid intake between treatment sessions.
Following hemofiltration, fluid balancing, and ultrafiltration, the blood is returned to the individual.
The invention provides hemofiltration systems and methods that circulate blood from an individual through a hemofilter to remove waste and to return blood and replacement fluid to the individual after removal of waste. The systems and methods maintain sterile extracorporeal processing conditions during and between therapy sessions.
According to one aspect of the invention, the systems and methods include a waste discharge path in the extracorporeal circuit to convey waste fluid to a waste receiving unit. The waste discharge path includes an air break. The air break prevents back flow of waste contaminants into the extracorporeal circuit from the waste receiving unit.
According to another aspect of the invention, the systems and methods include a replacement fluid path in the extracorporeal circuit to convey replacement fluid from a source to the extracorporeal circuit. The replacement fluid path includes a sterilizing filter to avoid contamination of the extracorporeal circuit.
Another aspect of the invention provides a hemofiltration system and method employing a hemofiltration machine including a chassis and at least one flow controlling element on the chassis. An extracorporeal circuit is provided for circulating blood from an individual through a hemofilter to remove waste and to return blood to the individual after removal of waste. A portion of the extracorporeal circuit is integrated, at least in part, within a flexible panel free of an air-fluid interface. A fluid processing cartridge orientes the flexible panel for mounting as an integrated unit on the chassis with the flexible panel in operating engagement with the flow controlling element and for removal as an integrated unit from the chassis. A controller for the hemofiltration machine is operable in a hemofiltration mode to operate the flow controlling element, when the fluid processing cartridge is mounted on the chassis, to convey an individual""s blood through the extracorporeal fluid circuit to a hemofilter to remove waste fluid and to supply replacement fluid. The controller is also operable in a dwell mode to suspend the hemofiltration mode and retain the fluid processing cartridge on the chassis between multiple intermittent hemofiltration sessions during a prescribed time period.
In one embodiment, during the dwell mode, the controller operates the flow controlling element to introduce a bacteriostatic agent into the extracorporeal circuit.
In one embodiment, during the dwell mode, the controller subjects the extracorporeal circuit to refrigeration.
In one embodiment, the controller registers use of the extracorporeal circuit and prevents operation of the hemofiltration machine when the registered use fails to correlate with predetermined criteria.
Other features and advantages of the inventions are set forth in the following specification and attached drawings.